Methods Tuohy needle is introduced into intervertebral space at the level of L3-L4 up to the interspinous ligaments ( nearly 2cm mark on the needle).A3-way stopcock is connected to the hub of Tuohy needle with the in-line port of the stopcock attached to an air-filled 10 ml syringe. Using a 75 cm extension tube set and create a 30 mm Hg pressure gradient between manometer and the tip of epidural needle , the needle is advanced slowly using both hands while monitoring the manometer reading and is stopped when the pressure suddenly dropped ( the pressure usually drops by 5-10 mm Hg when the tip of the needle inters the epidural space ).